github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fs/dirent_cache_test.go

// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package fs

import (
	"testing"
)

func TestDirentCache(t *testing.T) {
	const maxSize = 5

	c := NewDirentCache(maxSize)

	// Size starts at 0.
	if got, want := c.Size(), uint64(0); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// Create a Dirent d.
	d := NewNegativeDirent("")

	// c does not contain d.
	if got, want := c.contains(d), false; got != want {
		t.Errorf("c.contains(d) got %v want %v", got, want)
	}

	// Add d to the cache.
	c.Add(d)

	// Size is now 1.
	if got, want := c.Size(), uint64(1); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// c contains d.
	if got, want := c.contains(d), true; got != want {
		t.Errorf("c.contains(d) got %v want %v", got, want)
	}

	// Add maxSize-1 more elements.  d should be oldest element.
	for i := 0; i < maxSize-1; i++ {
		c.Add(NewNegativeDirent(""))
	}

	// Size is maxSize.
	if got, want := c.Size(), uint64(maxSize); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// c contains d.
	if got, want := c.contains(d), true; got != want {
		t.Errorf("c.contains(d) got %v want %v", got, want)
	}

	// "Bump" d to the front by re-adding it.
	c.Add(d)

	// Size is maxSize.
	if got, want := c.Size(), uint64(maxSize); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// c contains d.
	if got, want := c.contains(d), true; got != want {
		t.Errorf("c.contains(d) got %v want %v", got, want)
	}

	// Add maxSize-1 more elements.  d should again be oldest element.
	for i := 0; i < maxSize-1; i++ {
		c.Add(NewNegativeDirent(""))
	}

	// Size is maxSize.
	if got, want := c.Size(), uint64(maxSize); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// c contains d.
	if got, want := c.contains(d), true; got != want {
		t.Errorf("c.contains(d) got %v want %v", got, want)
	}

	// Add one more element, which will bump d from the cache.
	c.Add(NewNegativeDirent(""))

	// Size is maxSize.
	if got, want := c.Size(), uint64(maxSize); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// c does not contain d.
	if got, want := c.contains(d), false; got != want {
		t.Errorf("c.contains(d) got %v want %v", got, want)
	}

	// Invalidating causes size to be 0 and list to be empty.
	c.Invalidate()
	if got, want := c.Size(), uint64(0); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}
	if got, want := c.list.Empty(), true; got != want {
		t.Errorf("c.list.Empty() got %v, want %v", got, want)
	}

	// Fill cache with maxSize dirents.
	for i := 0; i < maxSize; i++ {
		c.Add(NewNegativeDirent(""))
	}
}

func TestDirentCacheLimiter(t *testing.T) {
	const (
		globalMaxSize = 5
		maxSize       = 3
	)

	limit := NewDirentCacheLimiter(globalMaxSize)
	c1 := NewDirentCache(maxSize)
	c1.limit = limit
	c2 := NewDirentCache(maxSize)
	c2.limit = limit

	// Create a Dirent d.
	d := NewNegativeDirent("")

	// Add d to the cache.
	c1.Add(d)
	if got, want := c1.Size(), uint64(1); got != want {
		t.Errorf("c1.Size() got %v, want %v", got, want)
	}

	// Add maxSize-1 more elements. d should be oldest element.
	for i := 0; i < maxSize-1; i++ {
		c1.Add(NewNegativeDirent(""))
	}
	if got, want := c1.Size(), uint64(maxSize); got != want {
		t.Errorf("c1.Size() got %v, want %v", got, want)
	}

	// Check that d is still there.
	if got, want := c1.contains(d), true; got != want {
		t.Errorf("c1.contains(d) got %v want %v", got, want)
	}

	// Fill up the other cache, it will start dropping old entries from the cache
	// when the global limit is reached.
	for i := 0; i < maxSize; i++ {
		c2.Add(NewNegativeDirent(""))
	}

	// Check is what's remaining from global max.
	if got, want := c2.Size(), globalMaxSize-maxSize; int(got) != want {
		t.Errorf("c2.Size() got %v, want %v", got, want)
	}

	// Check that d was not dropped.
	if got, want := c1.contains(d), true; got != want {
		t.Errorf("c1.contains(d) got %v want %v", got, want)
	}

	// Add an entry that will eventually be dropped. Check is done later...
	drop := NewNegativeDirent("")
	c1.Add(drop)

	// Check that d is bumped to front even when global limit is reached.
	c1.Add(d)
	if got, want := c1.contains(d), true; got != want {
		t.Errorf("c1.contains(d) got %v want %v", got, want)
	}

	// Add 2 more element and check that:
	//   - d is still in the list: to verify that d was bumped
	//   - d2/d3 are in the list: older entries are dropped when global limit is
	//     reached.
	//   - drop is not in the list: indeed older elements are dropped.
	d2 := NewNegativeDirent("")
	c1.Add(d2)
	d3 := NewNegativeDirent("")
	c1.Add(d3)
	if got, want := c1.contains(d), true; got != want {
		t.Errorf("c1.contains(d) got %v want %v", got, want)
	}
	if got, want := c1.contains(d2), true; got != want {
		t.Errorf("c1.contains(d2) got %v want %v", got, want)
	}
	if got, want := c1.contains(d3), true; got != want {
		t.Errorf("c1.contains(d3) got %v want %v", got, want)
	}
	if got, want := c1.contains(drop), false; got != want {
		t.Errorf("c1.contains(drop) got %v want %v", got, want)
	}

	// Drop all entries from one cache. The other will be allowed to grow.
	c1.Invalidate()
	c2.Add(NewNegativeDirent(""))
	if got, want := c2.Size(), uint64(maxSize); got != want {
		t.Errorf("c2.Size() got %v, want %v", got, want)
	}
}

// TestNilDirentCache tests that a nil cache supports all cache operations, but
// treats them as noop.
func TestNilDirentCache(t *testing.T) {
	// Create a nil cache.
	var c *DirentCache

	// Size is zero.
	if got, want := c.Size(), uint64(0); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// Call Add.
	c.Add(NewNegativeDirent(""))

	// Size is zero.
	if got, want := c.Size(), uint64(0); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// Call Remove.
	c.Remove(NewNegativeDirent(""))

	// Size is zero.
	if got, want := c.Size(), uint64(0); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}

	// Call Invalidate.
	c.Invalidate()

	// Size is zero.
	if got, want := c.Size(), uint64(0); got != want {
		t.Errorf("c.Size() got %v, want %v", got, want)
	}
}